<style>
    .box {
        /* 解耦、复用：提取公共部分 */
        width: 200px;
        height: 100px;
        border: 5px solid orange;
    }
    .red {
        /* width: 200px;
        height: 100px; */
        background-color: red;
    }
    .blue {
        /* width: 200px;
        height: 100px; */
        background-color: blue;
    }
</style>

<div class="box">测试001</div>
<div class="box red">测试002</div>
<div class="box blue">测试003</div>